Agronomy Journal 92:1149-1155 (2000)
© 2000 American Society of Agronomy
SOYBEAN
Evaluation of Seedbed Preparation, Planting Method, and Herbicide Alternatives for Dryland Soybean Production
Michael P. Poppa,
Lawrence R. Oliverb,
Carl R. Dillonc,
Terry C. Keislingd and
Patrick M. Manninge
a Dep. of Agric. Econ. and Agribusiness, 221 Agric. Building, Univ. of Arkansas, Fayetteville, AR 72701 USA
b Dep. of Crop, Soil, and Environ. Sci., 276 Altheimer Drive, Univ. of Arkansas, Fayetteville, AR 72701 USA
c Dep. of Agric. Econ., 403 Agric. Engineering Building no. 2, Univ. of Kentucky, Lexington, KY 40546-0276 USA
d Dep. of Crop, Soil, and Environ. Sci., Univ. of Arkansas Northeast Res. and Ext. Cent., P.O. Box 48, Keiser, AR 72351 USA
e Dep. of Agric. Econ. and Agribusiness, 221 Agric. Building, Univ. of Arkansas, Fayetteville, AR 72701 USA
mpopp{at}comp.uark.edu
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ABSTRACT
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The current economic situation provides incentives for producers to reduce input costs. Examples include reduced herbicide rates and an array of planting methods that utilize new herbicide and equipment technologies. This study investigated the implications of seedbed preparation (conventional vs. conservation tillage), planting equipment (broadcast, drill, no-till drill, air seeder, and planter), and herbicide alternatives [full-rate preplant followed by full-rate over the top (FRI), reduced-rate preplant followed by reduced-rate over the top (RRI), and full-rate over the top by itself (FROT)] for soybean [Glycine max (L.) Merr] at two locations (Keiser and Pine Tree, AR) with two cropping systems (full season vs. double-cropped). While some yield differences were observed across seedbed preparation and planting equipment, they did not lead to consistent results. Conventional and conservation tillage were the preferred production strategies for full-season and double-cropped systems, respectively. Seasonal labor, weather, and scale of operation are expected to play a major role because planting equipment did not impact yields or cost. Herbicide programs did not affect yields. Lower costs through reduced-rate herbicide applications led to higher returns and lower financial risk without restricting the planting method. Both the FROT and RRI weed control systems lead to higher returns compared with the FRI system. Producers concerned with the lack of residual herbicide activity afforded by preplant herbicides would be expected to choose the RRI system at the cost of slightly lower net returns in the full-season system.
Abbreviations: CES, Arkansas Cooperative Extension Service • FRI, full-rate preplant and over-the-top herbicide applications • FROT, full rate over-the-top herbicide applications • GLM, General Linear Models • GMO, genetically modified organism • IT, implement train • MSBG, Mississippi State Budget Generator • OT, over the top • PPI, preplant incorporated • RRI, reduced-rate preplant and over-the-top herbicide applications
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INTRODUCTION
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CHANGES IN FARM LEGISLATION, increasing input prices, and concerns over agriculture's environmental impacts have presented new challenges for producers in recent years. One way to meet these challenges is to find ways to reduce variable costs while maintaining or increasing profitable yield levels. The major categories of variable costs in soybean production are seedbed preparation, planting, weed control, and harvesting. Variable costs are being reduced with strategies such as reduced- and no-tillage practices, reduced-rate herbicide applications, and alternative planting methods that may affect the scale of operation, seasonal labor requirements, and offer additional flexibility in the scheduling of operations before and during planting.
Conservation tillage practices work well in certain environments and are now commonplace (Towery, 1998). Some studies on clayey soils and soils with high silt and low organic matter have indicated that some soil tillage at or just before planting can be advantageous. However, the yield effect of this tillage ranges from approximately 0 to 336 kg ha-1 depending on the soil types and weather scenarios (Oriade et al., 1999).
New equipment, such as high residue implements and air seeders, have made the combination of field operations possible. This would have farm-specific implications for coordination and scheduling of planting operations because different equipment alternatives are expected to affect the scale of the operation via daily equipment planting capacity, seasonal labor requirements, short-term weather forecasts, and choice of herbicide technology (Robinson et al., 1984).
Weed control systems have undergone a transition over the past decade. Preplant-incorporated (PPI) herbicides, followed by postemergence applications targeted at specific weed species, were recommended for consistent weed control in the past. Broader spectrum herbicide chemistries that can be applied over the top (OT) now afford more planting alternatives. For example, OT applications have made drill (narrow-row) and broadcast production systems practical. One area of concern with the OT system is the lack of residual herbicidal activity that would otherwise be available, especially from the PPI applications. However, on fields with high soybean populations, the competitiveness of the soybean crop itself can provide needed suppression of weed seedlings. In fact, if soybean is weed free at 14 to 28 d after emergence (at the time of complete canopy development), the competitiveness of the crop is sufficient to suppress almost all annual weeds (Adcock et al., 1990).
Given the lack of residual herbicide activity without PPI herbicides, another alternative for reducing weed control costs is the use of reduced-rate PPI herbicide applications. Reduced-rate herbicide technology has been investigated in depth for several chemicals, diverse locations, and weed species (Baldwin et al., 1988; DeFelice et al., 1989; Devlin et al., 1991; Prostko and Meade, 1993; King and Oliver, 1992). The results have shown that some herbicides are very effective at reduced rates for some weed species. Usually the age of the weed and the environmental conditions at the time of application determine how much the rates can be reduced (Baldwin et al., 1991). Reduced rates can also result in decreased soybean injury (Buhler et al., 1992) and may lead to less weather-related production risk than systems that rely on good weather for timely OT application after planting.
Weed control discussion has also centered on genetically modified organism (GMO) seed varieties that afford simplified weed control, and thus possibly make the above discussion a moot point. The GMO soybean seed varieties in Arkansas typically involve a comparison of environmental benefits, ease of application, seed costs (due to technology fees), reliance on a single product in terms of cost and weeds controlled, a time lag in yield potential for GMO seed varieties, and questionable consumer acceptance (Oriade et al., unpublished data, 1999). Due to the number of potential drawbacks with the use of GMO seed varieties, a discussion of more conventional herbicide-treatment alternatives is still appropriate.
The objectives of this study were to evaluate the economic feasibility and relative profitability of various combinations of two seedbed preparation methods using five planting-equipment alternatives and three herbicide regimes in a full-season dryland soybean system at two locations with a double-cropped soybean system at one of the locations. This resulted in a diverse set of eight planting method alternatives for each location and a cropping system that would suit a variety of producer profiles in terms of scale of operation, equipment use, herbicide choice, and seasonal labor requirements. The results are expected to reveal whether there are significant differences in yield and net returns above the total specified cost across seedbed preparation method and planting-equipment alternative. Further, the results are expected to show how robust and effective reduced-rate herbicide programs are across the different planting methods (combinations of seedbed preparation and planting equipment).
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Materials and methods
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Agronomic
This study was conducted during the crop years of 1995 through 1997 at the University of Arkansas Northeast Research and Extension Center (NEREC) in Keiser, AR and the Pine Tree Branch Experiment Station near Colt, AR. Soil series were Sharkey silty clay (Clayey over loamy, smectitic, acid, thermic Vertic Epiaquept) at Keiser and Calloway silt loam (fine-silty, mixed, active, thermic Glossaquic Fragiudalf) at Pine Tree. The treatment design was a split-split plot with three replications. Main plots were preplant tillage. The first split was planting equipment. The second split was herbicide program. Soybeans were grown in a full-season system at both locations. At Pine Tree, a double-cropped system of soybean following winter wheat (Triticum aestivum L.) was also evaluated.
Two preplant tillage methods were used: Conventional and conservation. Conventional plots were tilled before planting and again at planting. Conservation tillage plots were disturbed only if dictated by the planting method. The five different planting-equipment alternatives included: (i) broadcast planting, in which seed were scattered on the soil surface and incorporated with a disk; (ii) conventional drill for conventionally prepared seedbeds; (iii) no-till drill for conservation tillage plots; (iv) standard planter on conventionally prepared seedbeds; and (v) an implement train (IT) consisting of a high residue field cultivator (for tillage), followed by an air seeder (for seeding), followed by a rolling basket (for soil conditioning). The IT equipment set up offered additional alternatives such as a spray boom that could be attached to apply herbicides while planting, thereby eliminating another trip across the field. Preplant, planting, and postplant operations are shown in Table 1
. `Hutcheson' was used for all locations and planting dates. Seeding rates varied according to recommendations from the Arkansas Cooperative Extension Service (CES).
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Table 1 Field operations by herbicide program, planting equipment, and seedbed preparation method for all locations and cropping systems
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In addition to altering the planting method, three herbicide programs were used in the experiment (Tables 2 and 3)
. The first was an FRI program, which entailed the use of PPI herbicides at the labeled rate, followed by an OT application of herbicides at the labeled rate. The second was an RRI program, which continued the use of PPI herbicides, but at reduced rates, and was followed by a reduced-rate OT application. The third herbicide program differed from the first in that no PPI herbicides were used.
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Table 2 Herbicide applications by herbicide program, seedbed preparation, and planting equipment for all locations and cropping systems
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Economic
The economic analysis was based on enterprise budgets generated by the Mississippi State Budget Generator (MSBG) (Spurlock and Laughlin, 1992). A total of 48 enterprise budgets were generated for each combination of tillage method, planting-equipment alternative, herbicide program, and cropping system in the study. Four of the five equipment alternatives were used under each tillage method, each with three herbicide programs in two cropping systems. Therefore, 12 budgets each were generated for conventionally prepared seedbeds and conservation tillage plots in both full-season and double-cropped dryland soybean production systems. Due to the number of replications in the experiment, the MSBG was used to calculate only direct and fixed expenses while the net returns (returns to land, labor, and management) were calculated using a spreadsheet. Enterprise budgets were developed using yields, input requirements, and field operations obtained from the records of the agronomic experiment and CES recommendations.
Price, production, and cost data were chosen to be representative of the 1996 crop year because 1996 represented the middle year of the study. A 5-yr (1992–1996) average statewide soybean price of $0.235 kg-1 was used to calculate gross receipts (Arkansas Agric. Statistics Serv., 1997). The average price was used to eliminate any market effects from years with abnormally high or low prices. The input prices included in the MSBG version that was issued by the CES were used for the field operations. Further, CES budgets reflective of the 1996 crop year were used as guidelines for common production practices included in the budgets of this study (Brown and Windham, 1997).
Only operations (rather than specific equipment specifications) for the different planting methods are detailed in Table 1 because a study of the scale of operation and seasonal labor requirements associated with the different equipment alternatives is beyond the scope of this paper. Further, the economic implications of the different equipment alternatives are restricted to reporting the returns above total specified costs that are calculated as sales less than direct costs of seed, fertilizer, custom work, hired labor, herbicides, fuel, repair and maintenance, operating interest, and hauling expenses as well as fixed costs of depreciation and opportunity cost on equipment. These returns may be interpreted as returns to land, labor, and management. Fixed costs were included to reflect the length of run that decision makers would use to make choices about seedbed preparation and planting equipment.
Breakeven analysis was conducted for prices and yields above the total specified expenses to gain a broader perspective of the economic implications of the various tillage, planting, and herbicide combinations. Specifically, the breakeven analysis allows some assessment of the risk associated with yield and total specified cost differences across the various treatments.
Sensitivity analysis was conducted for the net returns above the total specified costs by changing soybean prices. Like the breakeven analysis, this was done to ascertain the range in returns due to changes in output price that were associated with the herbicide treatments. The sensitivity analysis shows how much net returns will change in response to soybean price changes while the breakeven analysis shows the minimum price or yield a producer can sustain with a particular treatment.
Statistical Analysis
Statistical analysis was performed using the Statistical Analysis System (SAS). The General Linear Models (GLM) procedure was used to analyze the grain yield and net returns (SAS Inst., 1989). The GLM procedure was used because of missing yield data for several treatments in various replications. The model utilized yield and net returns above the total specified costs as dependent variables. The independent variables and results of the statistical analysis are shown in Table 4
. Formulas for computing split-split plot LSDs were taken from Little and Hills (1978)(p. 101–114).
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Table 4 Summary of analysis of variance on yield and net returns above the total specified cost by location and cropping system
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Results and discussion
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Agronomic
At Pine Tree, the drill and air-seeder planting methods resulted in a density that was approximately 10 plants m-2 higher than the densities from the planter and broadcast methods. The difference was due to the calibration of the seeding rate at planting (Table 1). On the silt loam, tillage practice did not influence soybean stand. On the heavy clay at Keiser, broadcasting seed onto a no-till surface followed by disking resulted in a lower stand than broadcasting onto a tilled surface. In the no-till clay, soil-seed contact was poor. Weed control programs did not influence soybean stand at either location.
The dominant weeds were broadleaf signalgrass [Brachiaria platyphylla (Griseb.) Nash] at Pine Tree and pitted morningglory (Ipomoea lacunosa L.) at Keiser. Weed control was deemed adequate for all planting methods with each herbicide program. Soybean yield on the low water-holding silt loam at Pine Tree was approximately one-half of the yield obtained on the high water-holding clay soil at Keiser (Table 5)
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Table 5 Soybean yields by planting method for all locations and cropping systems averaged across herbicide programs by year
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Tillage or seedbed preparation had only a limited impact (Table 4). Significant effects were only observed in the double-cropped system and varied by year. Specifically, conventional tillage yields in the double-cropped system were significantly higher than conservation tillage yields in 1996 and lower in 1997, respectively (Table 5). No other consistent, significant differences were observed from tillage method in other years or in the full-season system.
Planting-equipment alternatives had a more significant impact than seedbed preparation. Significant differences in yields were observed across both the full-season and double-cropped systems at both locations (Table 4). Results were again affected by year. No statistically significant, top-performing planting equipment could be identified although there were a number of significant differences across planting equipment in any given year. This implies that producers may have to look to criteria other than yield to make their planting-equipment decisions.
Finally, the herbicide program provided a statistically significant impact in terms of yield only in conjunction with tillage and seedbed preparation in the double-cropped system (Table 4). The PPI herbicide programs (FRI and RRI) had residual herbicide activity, which was activated at incorporation or initial rainfall following planting. While this had the effect of reducing some weather-related risk associated with herbicide activation, it did not play an important role because timely application of OT herbicides for the FROT program was nonproblematic in this trial.
Economic
While yields did not vary significantly across tillage treatment, planting method, or herbicide program, the net returns above the total specified expenses were affected by all three (Table 4). Tillage was not significant for the full-season system at both locations (except for 1997 at Pine Tree, Table 6)
even though on average, conventional tillage showed average returns that were slightly higher than those from conservation tillage across all planting-equipment alternatives and study years. For the double-cropped system, the no-till option performed better than conventional tillage in 1995 and 1997 but not in 1996. Looking at the net returns above the total specified expenses in Table 6, no clear evidence points to a superior seedbed preparation method.
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Table 6 Soybean net returns above the total specified expenses by planting method for all locations and cropping systems averaged across herbicide programs by year
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Planting-equipment recommendations on the basis of net returns lead to no clear choice across all locations or cropping systems; this is evident in the few statistically significant differences across planting methods. For practical purposes, this means that all planting methods are equivalent. Therefore, a producer's choice of planting equipment is more likely to be influenced by seasonal labor and weather constraints, scale of operation, and interrelationships with planting needs for other crops than by crop yield or profitability differences. For example, a producer facing a situation of having to plant 150 ha in 1 d because of impending poor weather, may opt to broadcast rather than use a planter.
The herbicide program changed direct expenses at all locations, with subsequent changes in the net returns above direct expenses (Table 7)
. The highest direct cost was for the FRI program. The next highest was the RRI program, and the least expensive was the FROT program. Note that the Duncan rankings reflect that yield was not significantly impacted by the herbicide program as previously noted, and the direct-expense differential across the herbicide programs leads to a consistent top performance of the RRI and FROT programs over the FRI program at all locations in terms of the net returns above direct costs. Including the fixed expenses of depreciation and opportunity cost of capital tied up in equipment did not affect this ranking.
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Table 7 Comparison of herbicide programs by yield, total direct expense, net returns above total direct expense, total specified expense, and net returns above total specified expense averaged across all planting and seedbed preparation methods, 1995 to 1997
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Coupled with the previous two results on seedbed preparation and planting-equipment choice, the conclusions for reduced-rate herbicide applications are clear. Preplant-incorporated herbicides may be applied at reduced rates or eliminated to obtain higher profits without narrowing the choice of seedbed preparation or planting-equipment alternatives. Producers that are concerned with the lack of residual herbicide activity afforded by PPI herbicides would be expected to choose the RRI program at the cost of slightly lower net returns, at least in the full-season system.
The breakeven prices above the total specified expenses (Table 8) , a function of both yield and the total specified expenses, varied little across planting-equipment alternatives and seedbed preparation method. Because yields did not differ significantly across treatments at each location and cropping system, the breakeven prices are mostly driven by cost differences, which are reflected in the lower breakeven prices for the RRI and FROT herbicide programs. Location differences were driven by yield, whereas cropping-system differences were a function of differences in herbicide costs. Therefore, reduced-rate herbicide applications not only increase profitability by lowering costs, but they also lower the financial risk of losses in low price years. Given this discussion, producers may be expected to use conventional tillage for the full-season system and conservation tillage when growing soybean in rotation with winter wheat. The breakeven yields above the total specified expenses ranged between 873 and 1290 kg ha-1. Results are not reported in detail because the same conclusions were already drawn from the breakeven price analysis.
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Table 8 Breakeven price above total specified expenses by seedbed preparation method, herbicide program, location, and cropping system averaged across all planting equipment alternatives and years
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A sensitivity analysis on price showed that the net returns above the total specified costs were less sensitive to the price changes at Keiser than those from either system at Pine Tree. This was expected, given the relatively better yields and net returns at Keiser. Therefore, producers at Pine Tree would be expected to scrutinize their herbicide-program decisions more carefully than those at Keiser. The sensitivity analysis also confirmed the finding that the FROT program carries the least amount of financial risk relative to the other programs because the output price changes affect the net returns to a lesser degree with the RRI and FROT programs when compared with the higher-cost FRI alternative.
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Summary and conclusions
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An agronomic experiment was conducted at two Arkansas locations during the 1995 to 1997 crop years to examine the feasibility of using reduced inputs in soybean production. Using data from this study, economic analysis was performed to determine the relative economic feasibility and profitability of various combinations of two cropping systems, two seedbed preparation methods, five planting equipment alternatives and three herbicide programs. It was hypothesized that net returns above total specified costs from treatments using reduced inputs would be similar to the net returns above total specified costs of conventional treatments such as the FRI herbicide program.
In conclusion, the data suggest that the FROT herbicide program, by lowering input costs, reduces financial risk, increases net returns and does not restrict the producer's choice of planting equipment and seedbed preparation alternatives. Net returns above total specified costs increased anywhere from $47 to $73 ha-1 by at least partially eliminating PPI herbicide applications. Producers at Keiser enjoy higher yields and net returns and are therefore expected to scrutinize their herbicide choice less than producers at Pine Tree. The double-cropped system, with lesser needs for herbicides on seedbeds prepared using conservation tillage, was the only system sensitive to seedbed preparation in terms of net returns. Planting equipment alternatives did not affect yield or net returns above total specified costs in a consistent manner.Arkansas Agricultural Statistics Service 1997; SAS Institute 1989
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ACKNOWLEDGMENTS
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The authors acknowledge the Arkansas Soybean Promotion Board for financial support; Marliss, John Deere, Gandy, and DMI for providing the equipment necessary for these experiments; Graduate assistants Scott Hill and Jon Meisner and research specialist Alan Pearce; the staff of the Northeast Research and Extension Center and the Pine Tree Branch Experiment Station; and the weed science graduate students for their oversight and help in carrying out the experiments.
Received for publication September 9, 1999.
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REFERENCES
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- Adcock T.E., Banks P.A., Bridges D.C. Effects of preemergence herbicides on soybean (Glycine max) weed competition. Weed Sci. 1990;38:108-112.
- Arkansas Agricultural Statistics Service. 1997. Arkansas agricultural statistics for 1996. Univ. of Arkansas Coop. Ext. Serv. Publ. 393.
- Baldwin, F.L., J.W. Boyd, and C.B. Guy. 1991. Recommended chemicals of weed and brush control. Univ. of Arkansas Coop. Ext. Serv. Publ. 44.
- Baldwin F.L., Oliver L.R., Tripp T.N. Arkansas experience with reduced rate herbicide recommendations. Proc. South. Weed Sci. Soc. 1988;41:308.
- Brown, C.D., and T.E. Windham. 1997. Soybeans, early season nonirrigated, loamy soils, Arkansas. Arkansas Coop. Ext. Serv. Enterprise Budget AG-491-11-97.
- Buhler D.D., Gunsolus J.L., Ralston D.F. Integrated weed management to reduce herbicide inputs in soybean. Agron. J. 1992;84:973-978.[Abstract/Free Full Text]
- DeFelice M.S., Brown W.B., Aldrich R.J., Sims B.D., Judy D.T., Guethle D.R. Weed control in soybeans (Glycine max) with reduced rates of postemergence herbicides. Weed Sci. 1989;37:365-374.
- Devlin D.L., Long J.H., Maddux L.D. Using reduced rates of postemergence herbicides in soybeans (Glycine max). Weed Technol. 1991;5:834-840.
- King C.A., Oliver L.R. Application rate and timing of acifluorfen, bentazon, chlorimuron, and imazaquin. Weed Technol. 1992;6:526-534.
- Little T.M., Hills F.J. Agricultural experimentation. New York: John Wiley & Sons, 1978.
- Oriade C.A., Dillon C.R., Keisling T.C. Economics of wheat residue management in doublecrop soybean. J. Prod. Agric. 1999;12:42-48.
- Prostko E.P., Meade J.A. Reduced rates of postemergence herbicides in conventional soybeans (Glycine max). Weed Technol. 1993;7:365-369.
- Robinson E.L., Langdale G.W., Stuedemann J.A. Effects of three weed control regimes on no-till and tilled soybeans. Weed Sci. 1984;32:17-19.
- SAS Institute. SAS/STAT user's guide. Cary, NC: Version 6. 4th ed. SAS Inst, 1989.
- Spurlock, S.R., and D.H. Laughlin. 1992. Mississippi state budget generator user's guide. Version 3.0. Mississippi Agric. and Forest Exp. Stn. Agric. Econ. Tech. Publ. 88.
- Towery, D. 1998. Conservation tillage report `troubling' for U.S. agriculture [Online]. Conservation Technology Information Center news release. Available at http://www.ctic.purdue.edu/Core4/CT/CTsurvey/AgTroubling.html (verified 28 Jan. 2000).
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ABSTRACT
INTRODUCTION
